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Few clades of plants have proven as difficult to classify as cacti. One explanation may be an unusually high level of convergent and parallel evolution (homoplasy). To evaluate support for this phylogenetic hypothesis at the molecular level, we sequenced the genomes of four cacti in the especially problematic tribe Pachycereeae, which contains most of the large columnar cacti of Mexico and adjacent areas, including the iconic saguaro cactus (Carnegiea gigantea) of the Sonoran Desert. We assembled a high-coverage draft genome for saguaro and lower coverage genomes for three other genera of tribe Pachycereeae (Pachycereus, Lophocereus, and Stenocereus) and a more distant outgroup cactus, Pereskia. We used these to construct 4,436 orthologous gene alignments. Species tree inference consistently returned the same phylogeny, but gene tree discordance was high: 37% of gene trees having at least 90% bootstrap support conflicted with the species tree. Evidently, discordance is a product of long generation times and moderately large effective population sizes, leading to extensive incomplete lineage sorting (ILS). In the best supported gene trees, 58% of apparent homoplasy at amino sites in the species tree is due to gene tree-species tree discordance rather than parallel substitutions in the gene trees themselves, a phenomenon termed “hemiplasy.” The high rate of genomic hemiplasy may contribute to apparent parallelisms in phenotypic traits, which could confound understanding of species relationships and character evolution in cacti.

Se describe y compara la morfo-anatomía de plántulas de la tribu Pachycereeae con el objetivo de establecer diferencias entre las fases del crecimiento inicial y establecimiento y distinguir así la diferenciación entre plántula e individuo juvenil. El registro de los cambios morfo-anatómicos se obtuvo de una muestra de más de 500 plántulas de seis especies representantes de cinco géneros de esta tribu, de las cuales se tomaron semanalmente tres plántulas durante los tres primeros meses y posteriormente cada mes hasta completar 24 meses de crecimiento, con el propósito de registrar sus cambios morfo-anatómicos. Se encontraron diferencias (P < 0.05) para altura de la plántula, longitud de la raíz, altura y diámetro del tallo entre las especies en las diferentes edades. El retardo en el desarrollo del tallo y la raíz fue característico de Escontria chiotilla y Myrtillocactus geometrizans provenientes de semillas pequeñas. Las especies comparten atributos de los tejidos dérmico, fundamental y vascular, pero se destacan los cuerpos de proteína en Pachycereus grandis y los cristales prismáticos en epidermis-hipodermis de las especies de Neobuxbaumia. Al establecerse el cámbium vascular sólo se diferencian elementos de vaso y traqueidas de banda ancha, y las fibras aparecen hasta después del año de edad en algunas especies. Se concluye que la desaparición de cotiledones, presencia de costillas, establecimiento de cámbium vascular, mayor acumulación de xilema secundario y diferenciación de haces vasculares medulares permiten establecer el límite entre la etapa de plántula y planta joven en Pachycereeae.

 Premise of the study : Cactaceae is one of the most charismatic plant families because of the extreme succulence and outstanding diversity of growth forms of its members. Although cacti are conspicuous elements of arid ecosystems in the New World and are model systems for ecological and anatomical studies, the high morphological convergence and scarcity of phenotypic synapomorphies make the evolutionary relationships and trends among lineages diffi cult to understand.  Methods : We performed phylogenetic analyses implementing parsimony ratchet and likelihood methods, using a concatenated matrix with 6148 bp of plastid and nuclear markers ( trnK/matK , matK , trnL-trnF , rpl16 , and ppc ). We included 224 species representing approximately 85% of the family ’ s genera. Likelihood methods were used to perform an ancestral character reconstruction within Cactoideae, the richest subfamily in terms of morphological diversity and species number, to evaluate possible growth form evolutionary trends.  Key results : Our phylogenetic results support previous studies showing the paraphyly of subfamily Pereskioideae and the monophyly of subfamilies Opuntioideae and Cactoideae. After the early divergence of Blossfeldia, Cactoideae splits into two clades: Cacteae, including North American globose and barrel-shaped members, and core Cactoideae, including the largest diversity of growth forms distributed throughout the American continent. Para- or polyphyly is persistent in different parts of the phylogeny. Main Cactoideae clades were found to have different ancestral growth forms, and convergence toward globose, arborescent, or columnar forms occurred in different lineages.  Conclusions : Our study enabled us to provide a detailed hypothesis of relationships among cacti lineages and represents the most complete general phylogenetic framework available to understand evolutionary trends within Cactaceae.

A comprehensive taxonomic revision of the genus Pachycereus (Cactaceae, Cactoideae, Pachycereeae) is presented. Pachycereus is characterized by one synapomorphic character, the presence of a narrow interareolar groove, and by the combination of flowering region differentiated with flexible spines, flower with a narrow region between the pericarpel and the receptacular tube and the occurrence of trichomes and short spines in the pericarpel. Five species are recognized in the present treatment. One species (P. pecten-aboriginum) is widely distributed from Chihuahua in northern Mexico to Chiapas, three species (P. grandis, P. pringlei, and P. weberi) are restricted to defined floristic provinces, and one species (P. tepamo) is endemic to Depresion del Balsas. A key and descriptions of the species, based on herbarium specimens, field observations and intensive field collection are presented. The taxonomic history, synonymies, distribution, uses, and representative specimens are included. Three new combinations, Pterocereus gaumeri subsp. foetidus, Lemaireocereus lepidanthus, and Lophocereus marginatus, are proposed.

Dada la importancia natural y cultural de las cactáceas columnares en México, en una localidad mixteca con uso y manejo centenario de pitaya (Stenocereus pruinosus), se estudió su clasificación infraespecífica tradicional, los móviles de selección y la variación morfológica de 41 caracteres de tallo, flor y fruto en 15 variantes, mediante componentes principales y conglomerados. Informantes clave identificaron 25 cultivares (10 los más populares); los móviles de selección tradicionales son más diversos que los actuales comerciales, involucran más de 10 caracteres de fruto, tallo y producción. Tres componentes principales explicaron el 55 % de la variación evaluada y un agrupamiento adecuado definió cinco grupos de cultivares, según el tamaño y peso de fruto, el número y longitud de espinas del fruto y el número y tamaño de semillas. Se distinguieron tres tendencias de selección: frutos grandes y pesados, espinas abundantes y largas, espinas cortas y pocas. Otros caracteres que también son objeto de selección por los productores son el rendimiento por planta, época de cosecha, firmeza de cáscara y contenido de humedad del fruto.

Chromosome numbers for a total of 54 individuals representing 13 genera and 40 species of Cactaceae, mostly in tribe Trichocereeae, are reported. Five additional taxa examined belong to subfamily Opuntioideae and other tribes of Cactoideae (Browningieae, Pachycereeae, Notocacteae, and Cereeae). Among Trichocereeae, counts for 35 taxa in eight genera are reported, with half of these (17 species) for the genus Haageocereus. These are the first chromosome numbers reported for 36 of the 40 taxa examined, as well as the first counts for the genus Haageocereus. Both diploid and polyploid counts were obtained. Twenty nine species were diploid with 2n=2x=22. Polyploid counts were obtained from the genera Espostoa, Cleistocactus, Haageocereus, and Weberbauerocereus; we detected one triploid (2n=3x=33), nine tetraploids (2n=4x=44), one hexaploid (2n=6x=66), and three octoploids (2n=8x=88). In two cases, different counts were recorded for different individuals of the same species (Espostoa lanata, with 2n=22, 44, and 66; and Weberbauerocereus rauhii, with 2n=44 and 88). These are the first reported polyploid counts for Haageocereus, Cleistocactus, and Espostoa. Our counts support the hypothesis that polyploidy and hybridization have played prominent roles in the evolution of Haageocereus, Weberbauerocereus, and other Trichocereeae.

Anatomical variation in radial and longitudinal wood in Neobuxbaumia tetetzo was studied in four monopodic individuals. Vascular bundles in the radial direction from the pith to the vascular cambium and in the longitudinal direction from the base to the stem apex were analysed. Except for vessel density in the radial direction, the anatomical characters studied showed a pattern of cambial maturation similar to those reported for other angiosperms. The patterns of fiber anatomical variation show higher mechanical strength in the lower part of the stem, while the increase in vessel diameter towards the vascular cambium produces a positive relationship between plant water demands and larger size.

The phylogenetic relationships of Peniocereus (Cactaceae) species were studied using parsimony analyses of DNA sequence data. The plastid rpl16 and trnL-F regions were sequenced for 98 taxa including 17 species of Peniocereus, representatives from all genera of tribe Pachycereeae, four genera of tribe Hylocereeae, as well as from three additional outgroup genera of tribes Calymmantheae, Notocacteae, and Trichocereeae. Phylogenetic analyses support neither the monophyly of Peniocereus as currently circumscribed, nor the monophyly of tribe Pachycereeae since species of Peniocereus subgenus Pseudoacanthocereus are embedded within tribe Hylocereeae. Furthermore, these results show that the eight species of Peniocereus subgenus Peniocereus (Peniocereus sensu stricto) form a well-supported clade within subtribe Pachycereinae; P. serpentinus is also a member of this subtribe, but is sister to Bergerocactus. Moreover, Nyctocereus should be resurrected as a monotypic genus. Species of Peniocereus subgenus Pseudoacanthocereus are positioned among species of Acanthocereus within tribe Hylocereeae, indicating that they may be better classified within that genus. A number of morphological and anatomical characters, especially related to the presence or absence of dimorphic branches, are discussed to support these relationships.

Perforated ray cells are reported for the first time for 16 species of seven genera of Pachycereeae. The perforated ray cells are shorter than vessel elements and have simple perforation plates and small alternate intervascular pits. Among Cactaceae these specialised cells seem to be related with splitting of the tall rays.

Simple and multivariate linear models were used to demonstrate the influence of mechanical design and climate on stem morphology and branching architecture in 25 species of North American columnar cacti. The effect of phyletic inertia was tested by the method of independent contrasts. Stem girth was found to increase significantly slower with increased height within taxa (cross-sectional stem area ;ps [plant height] 0.603), than across taxon (cross-sectional stem area ;ps [plant height] 1.451). Juveniles are shown to be mechanically overbuilt and subsequently grow into more slender adult forms determined in part by structural limitations and the optimization of other stem functions. We make a structural analogy of relatively rigid columnar cacti to concrete columns and compare plants and models with similar growth forms lacking woody skeletons (barrel cacti). Taxa with woody support achieved a surface-to-volume ratio six times greater than taxa without woody support. Across taxon, cooler winter temperatures were associated with larger stem girths, and greater annual precipitation was associated with less frequent branching. The relationship between total plant surface and volume approaches isometry within taxa, but across taxon average individuals are scaled replicates. We hypothesize that architecture and average plant height are adjusted, in an evolutionary sense, to maintain geometric similitude between surface and volume along a climatic gradient.

The purpose of this study was to assess the phylogenetic relationships between tribes Cereeae and Browningieae in the cactus subfamily Cactoideae. During field trips to Venezuela, Ecuador and Chile, tissue samples were collected from representative specimens in natural populations. Monvillea* diffusa, M. maritima, and M. smithiana were virtually identical anatomically and, although similar to Cereus hexagonus, they were distinct in having large druses in their outer hypodermis and extremely small wall crystals in their cortex. Pilosocereus mortensenii was indistinguishable from the samples of Subpilocereus* (S. ottonis, S. repandus, S. russelianus) but was very different from other pilosocerei (P. lanuginosus, P. moritzianus, P. tillianus). Samples of Subpilocereus, including P. mortensenii, were similar to those of C. hexagonus in having no hypodermal crystals, no druses in pith or cortex, few or no mucilage cells in pith or cortex. Anatomical characters supported a hypothetical close relationship between Armatocereus (A. brevispinus, A. cartwrightianus, A. godingianus) and Jasminocereus (J. thouarsii), but Jasminocereus had few distinctive features that could be used to link it strongly to any genus in this study. Both tribes were variable, but members of each resembled each other more than they resembled any member of the other tribe. Leptocereus quadricostatus (tribe Echinocereeae) did not obviously share more characters with one tribe versus the other. Pachycereeae are more similar to Cereeae than to Browningieae.

A bibliographical and herbarium investigation on the pollination syndrome of Mexican columnar cacti (tribe Pachycereeae) was conducted. Most Mexican species of columnar cacti show a chiropterophilic-pollination syndrome and they flower synchronously in March to May. The floral biology, reproductive system and visitors (to both fruits and flowers) ofNeobuxbaumia tetetzo, the most abundant and dominant columnar cactus of succulent forest in the Tehuacan Valley, were studied. This species reached densities ofc.1200 individuals ha−1. The batsLeptonycteris curasoaeandChoeronycteris mexicanawere its only pollinators, whilst a more diverse array of visitors disperse seeds. Contrary to findings for multiple pollinators of columnar cacti in extratropical deserts in North America, the relationships betweenN. tetetzoand nectar-feeding bats was strong and tightly coupled in Mexico.

Microsatellite markers were developed for the columnar cactus Polaskia chichipe from central Mexico. After an enrichment procedure and three screening steps 87% of colonies contained microsatellites. A pair of primers for 10 loci (seven polymorphic) were developed, tested and used to estimate variation in samples of 18–45 individuals from the Tehuacan Valley, Mexico. Alleles per locus ranged from two to eight (mean 5.28; SD 2.5). Range of expected heterozygosity values was 0.188–0.797 (mean 0.502; SD 0.25). These loci are particularly useful for more precise evolutionary studies, such as gene flow and breeding systems, for this cactus species.

Cacti are a large and diverse group of stem succulents predominantly occurring in warm and arid North and South America. Chloroplast DNA sequences of the trnK intron, including the matK gene, were sequenced for 70 ingroup taxa and two outgroups from the Portulacaceae. In order to improve resolution in three major groups of Cactoideae, trnL-trnF sequences from members of these clades were added to a combined analysis. The three exemplars of Pereskia did not form a monophyletic group but a basal grade. The well-supported subfamilies Cactoideae and Opuntioideae and the genus Maihuenia formed a weakly supported clade sister to Pereskia. The parsimony analysis supported a sister group relationship of Maihuenia and Opuntioideae, although the likelihood analysis did not. Blossfeldia, a monotypic genus of morphologically modified and ecologically specialized cacti, was identified as the sister group to all other Cactoideae. The tribe Cacteae was found to be sister to a largely unresolved clade comprising the genera Calymmanthium, Copiapoa, and Frailea, as well as two large and well-supported clades. Browningia sensu stricto (excluding Castellanosia), the two tribes Cereeae and Trichocereeae, and parts of the tribes Notocacteae and Rhipsalideae formed one clade. The distribution of this group is largely restricted to South America. The other clade consists of the columnar cacti of Notocacteae, various genera of Browningieae, Echinocereeae, and Leptocereeae, the tribes Hylocereeae and Pachycereeae, and Pfeiffera. A large portion of this latter group occurs in Central and North America and the Caribbean.

Recent ecological research has revealed that the Sonoran Desert columnar cactus Lophocereus and the pyralid moth Upiga virescens form an obligate pollination mutualism, a rare but important case of coevolution. To investigate the phylogenetic origins of this unusual pollination system, we used molecular sequence data to reconstruct the phylogeny of the four taxa within the genus Lophocereus and to determine the phylogenetic position of Lophocereus within the North American columnar cacti (tribe Pachycereeae). Our analysis included Lophocereus, six Pachycereus species, Carnegiea gigantea, and Neobuxbaumia tetetzo within the subtribe Pachycereinae, and Stenocereus thurberi as an outgroup within the Stenocereinae. Extensive screening of chloroplast and mitochondrial genomes failed to reveal sequence variation within Lophocereus. At a deeper phylogenetic level, however, we found strong support for the placement of Lophocereus within Pachycereus as sister group to the hummingbird-pollinated P. marginatus. We discuss possible hypotheses that may explain the transition from bat pollination (ancestral) to moth and hummingbird pollination in Lophocereus and P. marginatus, respectively. Additional phylogenetic analyses suggest that the genus Pachycereus should be expanded to include Lophocereus, Carnegiea, Neobuxbaumia, and perhaps other species, whereas P. hollianus may need to be excluded from this clade. Future study will be needed to test taxonomic distinctions within Lophocereus, to test for parallel cladogenesis between phylogroups within Lophocereus and Upiga, and to fully delineate the genus Pachycereus and relationships among genera in the Pachycereinae.

Vivipary, the germination of seeds within the fruit prior to abscission from the maternal plant, is an important event in plants. Two main types of vivipary are known in vascular plants: true vivipary and pseudovivipary. In crop grasses, pseudovivipary is an undesirable character as it results in lower yields. To date, vivipary in the Cactaceae has been reported for less than 20 species, most of which are cultivated. Here, we report viviparous (cryptoviviparous—a subcategory of true vivipary) cacti in nature in members of the tribes Cacteae and Pachycereeae (subfamily Cactoideae). We present four species inhabiting coastal plains in areas subject to periodic flooding, namely, Ferocactus herrerae, Stenocereus alamosensis, S. thurberi, and Pachycereus schottii. These species from localities in northwestern Mexico had viviparous fruits and offspring in different stages of development. A potential trend in the data indicates that the overall proportion of viviparous plants is higher in coastal flooding areas relative to halophytic, nonflooding areas. In our view, vivipary is a reproductive strategy that has evolved to provide a more efficient mechanism favoring germination and new avenues for survival by contributing to population maintenance and short-distance dispersal on halophytic substrates.

Seed germination triggered by light exposure (positive photoblastism) has been determined in quantitative studies for numerous plant families and species. For Cactaceae, positive photoblastism is thought to be associated with life form and seed mass, but this association has never been evaluated. To explore hypotheses on associations between seed mass, seed dispersal, seed dormancy, life form, taxa and plant height with Relative Light Germination (RLG) in Cactaceae, we evaluated the effect of light on seed germination of 136 taxa. The taxa studied are native to several countries: México, Chile, Argentina, Brazil, Perú, USA, and Venezuela. Seed traits contrasted with RLG were life form, seed mass, seed dispersal, seed dormancy, adult plant height and taxon. We found some differences between RLG among taxa; Cacteae, Pachycereeae and Trichocereeae had higher RLG than Notocacteae. RLG was lower for seeds from taller than for shorter taxa, and lower for taxa with heavier seeds than for taxa with lighter seeds. Dispersal syndrome groups varied with RLG. RLG did not differ between cylindrical and globose taxa. Trends found here were in agreement with expectations for small-seeded species to have a light requirement to germinate more often than large-seeded species. This is the first time that cactus height is related to photoblastism. It is possible that seeds from tall plants are larger and thus have the capacity to produce taller seedlings than those from small plants, and that seedlings from large seeds with more resources have the ability to emerge from greater soil depths than those from small seeds. Fil: Flores, J.. Instituto Potosino de Investigación Científica y Tecnológica; México Fil: Jurado, E.. Universidad Autónoma de Nuevo León; México Fil: Chapa Vargas, L.. Instituto Potosino de Investigación Científica y Tecnológica; México Fil: Ceroni Stuva, A.. Universidad Nacional Agraria La Molina; Perú Fil: Dávila Aranda, P.. Universidad Nacional Autónoma de México; México Fil: Galindez, Guadalupe. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Recursos Naturales. Instituto de Recursos Biológicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gurvich, Diego Ezequiel. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: León Lobos, P.. Instituto de Investigaciones Agropecuarias; Chile Fil: Ordóñez, C.. Universidad Nacional Autónoma de México; México Fil: Ortega Baes, Francisco Pablo. Universidad Nacional de Salta. Facultad de Cs.naturales. Escuela de Agronomia. Laboratorio de Investigaciones Botanicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta; Argentina Fil: Ramírez Bullón, N.. Universidad Nacional Agraria La Molina; Perú Fil: Sandoval, A.. Instituto de Investigaciones Agropecuarias; Chile Fil: Seal, C. E.. Royal Botanic Gardens; Reino Unido Fil: Ullian, T.. Royal Botanic Gardens; Reino Unido Fil: Pritchard, H. W.. Royal Botanic Gardens; Reino Unido

"Se describe y compara la morfo-anatomía de plántulas de la tribu Pachycereeae con el objetivo de establecer diferencias entre las fases del crecimiento inicial y establecimiento y distinguir así la diferenciación entre plántula e individuo juvenil. El registro de los cambios morfo-anatómicos se obtuvo de una muestra de más de 500 plántulas de seis especies representantes de cinco géneros de esta tribu, de las cuales se tomaron semanalmente tres plántulas durante los tres primeros meses y posteriormente cada mes hasta completar 24 meses de crecimiento, con el propósito de registrar sus cambios morfo-anatómicos. Se encontraron diferencias (P < 0.05) para altura de la plántula, longitud de la raíz, altura y diámetro del tallo entre las especies en las diferentes edades. El retardo en el desarrollo del tallo y la raíz fue característico de Escontria chiotilla y Myrtillocactus geometrizans provenientes de semillas pequeñas. Las especies comparten atributos de los tejidos dérmico, fundamental y vascular, pero se destacan los cuerpos de proteína en Pachycereus grandis y los cristales prismáticos en epidermis hipodermis de las especies de Neobuxbaumia. Al establecerse el cámbium vascular sólo se diferencian elementos de vaso y traqueidas de banda ancha, y las fibras aparecen hasta después del año de edad en algunas especies. Se concluye que la desaparición de cotiledones, presencia de costillas, establecimiento de cámbium vascular, mayor acumulación de xilema secundario y diferenciación de haces vasculares medulares permiten establecer el límite entre la etapa de plántula y planta joven en Pachycereeae."

It has been suggested that there is a geographic dichotomy in the pollination systems of chiropterophilous columnar cacti: in intra-tropical areas they are pollinated almost exclusively by bats, whereas in extratropical areas they are pollinated by bats, birds and bees. However, currently the studies are clumped both taxonomically (mainly Pachycereeae species) and geographically (mainly in the Tehuacan Valley and the Sonoran Desert). This clumping limits the possibility of generalising the pattern to other regions or cactus tribes. Only four of the 36 chiropterophilous cacti in Pilosocereus have been studied. Despite the tropical distribution of two Pilosocereus species, bees account for 40-100% of their fruit set. We examined how specialised is the pollination system of P. leucocephalus in eastern Mexico. As we studied tropical populations, we expected a bat-specialised pollination system. However, previous studies of Pilosocereus suggest that a generalised pollination system is also possible. We found that this cactus is mainly bat-pollinated (bats account for 33-65% of fruit set); although to a lesser degree, diurnal visitors also caused some fruit set (7-15%). Diurnal visitors were more effective in populations containing honeybee hives. P. leucocephalus is partially self-compatible (14-18% of fructification) but unable to set fruit without visitors. Despite the variation in pollination system, P. leucocephalus shows more affinity with other columnar cacti from tropical regions than with those from extratropical regions. Although we report here that a new species of tropical Pilosocereus is relatively bat-specialised, this Cereeae genus is more flexible in its pollination system than the Pachycereeae genera.

• Background and Aims Chiropterophillous and ornithophillous characteristics can form part of a single reproductive strategy in plants that have flowers with diurnal and nocturnal anthesis. This broader pollination strategy can ensure seed set when pollinators are scarce or unpredictable. This appears to be true of hummingbirds, which presumably pollinate Marginatocereus marginatus, a columnar cactus with red nocturnal and diurnal flowers growing as part of dense bat-pollinated columnar cacti forests in arid regions of central Mexico. The aim of this study was to study the floral biology of M. marginatus, and evaluate the effectiveness of nocturnal vs. diurnal pollinators and the contribution of each pollinator group to overall plant fitness. • Methods Individual flower buds were marked and followed to evaluate flower phenology and anthesis time. Flowers and nectar production were measured. An exclusion experiment was conducted to measure the relative contribution of nocturnal and diurnal pollinators to seed set. • Key Results Marginatocereus marginatus has red hermaphroditic flowers with nocturnal and diurnal anthesis. The plant cannot produce seeds by selfing and was pollinated during the day by hummingbirds and during the night by bats, demonstrating that both pollinator groups were important for plant reproduction. Strong pollen limitation was found in the absence of one of the pollinator guilds. • Conclusions Marginatocereus marginatus has an open pollination system in which both diurnal and nocturnal pollinators are needed to set seeds. This represents a fail-safe pollination system that can ensure both pollination, in a situation of low abundance of one of the pollinator groups (hummingbirds), and high competition for nocturnal pollinators with other columnar cacti that bloom synchronously with M. marginatus in the Tehuacan Valley, Mexico.

Con el objetivo de ordenar y clasificar la diversidad morfológica del fruto de 31 variantes reconocidas por más de 20 cultivadores de pitaya [Stenocereus pruinosus (Otto) Buxb.] de la Mixteca Baja, México, se midieron 19 atributos morfológicos a 200 frutos (2 a 10 por variante). Los datos se analizaron mediante comparación de promedios, conglomerados y componentes principales. Los informantes identificaron las variantes por el color, tamaño y forma del fruto; tamaño y color de espina; tamaño y cantidad de semillas; dulzura, sabor y época de maduración. Aunque cinco atributos (grosor de cáscara, número de areolas, grosor y anchura de semilla y peso de pulpa/peso de cáscara) fueron significativamente iguales, el análisis multivariado apoya la pertinencia de 16 atributos para la caracterización de las variantes. Los tres primeros componentes principales (CP) resumieron el 60 % de la variación y ordenaron a las variantes por el tamaño y peso de fruto, y tamaño de semilla y espina (CP1), por el color de cáscara y pulpa (CP2) y por la redondez (CP3) del fruto, coincidiendo en gran parte con la clasificación infraespecífica tradicional. Un agrupamiento congruente con estos análisis define nueve grupos, uno de los cuales corresponde con un probable híbrido interespecífico. La clasificación empírica de los informantes es confirmada en gran parte por los análisis estadísticos

Resumen Se estudiaron los caracteres morfo-anatómicos y del metabolismo fotosintético en plántulas de Stenocereus queretaroensis (Weber) Buxb. para examinar dichos atributos durante su ontogenia. Más de 500 plántulas fueron sembradas en semilleros y durante los tres primeros meses fueron recolectadas cada semana; posteriormente cada mes hasta completar 56 semanas para registrar los cambios morfo-anatómicos. Parte de las plántulas se colectaron cada 3h durante 24h en los intervalos señalados y almacenaron en N2 líquido para estimar la concentración de ácido (protones titulables) por unidad de peso fresco. Las plántulas tuvieron un tallo de 3,6cm de altura con siete costillas y raíces de la misma longitud a las 56 semanas; al año los cotiledones se marchitaron. El eje hipocótilo-raíz, al igual que el tallo, tuvo epidermis simple y estomas escasos; la hipodermis también fue de un estrato y difiere del tallo adulto. El cámbium vascular se diferenció en plántulas de un año, el xilema secundario se diferencia del tallo adulto por la presencia de traqueidas de banda ancha y ausencia de fibras. Los protones titulables mostraron fluctuaciones irregulares en las primeras semanas de crecimiento, sin embargo, la acidez incrementó con la edad de las plántulas. En la semana 56 se incrementó a partir de las 18:00 y continuó hasta un valor máximo de 45,19µmolH+·g-1 de tejido a las 06:00 mostrando el patrón típico de metabolismo ácido de las crasuláceas. El rápido crecimiento de las raíces, la presencia de traqueidas de banda ancha y los escasos estomas se interpretaron como adaptaciones para evitar la desecación. Summary Morpho-anatomical characters and the photosynthetic metabolism of Stenocereus queretaroensis (Weber) Buxb. seedlings were studied to examine these features during their ontogeny. More than 500 seedlings were sowed in nurseries; during the first three months they were harvested every week and, thereafter, every month until completing 56 weeks, to record the morpho-anatomical changes. Some seedlings were collected every 3h during 24h at the mentioned time intervals and stored in liquid N2 to estimate the acid concentration (tritated protons) for unit of fresh weight. Seedlings had a shoot 3.6cm in height, with seven ribs, and roots with the same length after 56 weeks of age; cotyledons withered at one year old. The hypocotyl-root axis as well as the shoot had simple epidermis and scarce stomata; hypoderm was also of one layer and differs from the mature shoot. Vascular cambium developed in one year-old seedlings; secondary xylem was distinguished from the mature shoot by the occurrence of wide band tracheids and lack of fibers. The tritated protons showed irregular fluctuations during the first weeks of growth, however acidity increased with seedling age. In the week 56, the increment started at 18:00 reaching a maximum of 45.19µmolH+·g-1 tissue at 06:00, showing the typical crassulacean acid metabolism pattern. The rapid root growth, the occurrence of wide band tracheids and the scarce stomata were interpreted as adaptations to avoid drying. Resumo Estudaram-se os caracteres morfo-anatômicos e do metabolismo fotossintético em plântulas de Stenocereus queretaroensis (Weber) Buxb. para se examinar ditos atributos durante sua ontogenia. Mais de 500 plântulas foram semeadas em sementeiros e durante os três primeiros meses foram recolhidas cada semana; posteriormente cada mês até completar 56 semanas para registrar as mudanças morfo-anatómicas. Parte das plântulas se colheram cada 3h durante 24h nos intervalos assinalados e armazenaram em N2 líquido para estimar a concentração de ácido (prótons tituláveis) por unidade de peso fresco. As plântulas tiveram um caule de 3,6cm de altura com sete costelas e raízes da mesma longitude às 56 semanas; ao ano os cotiledones murcharam. O eixo hipocótilo-raíz, ao igual que o caule, teve epidermes simples e estomas escassos; a hipodermes também foi de um estrato e difere do caule adulto. O cámbium vascular se diferenciou em plântulas de um ano, o xilema secundário se diferencia do caule adulto pela presença de traqueidas de banda larga e ausência de fibras. Os prótons tituláveis mostraram flutuações irregulares nas primeiras semanas de crescimento, no entanto, a acidez incrementou com a idade das plântulas. Na semana 56 se incrementou a partir das 18:00 e continuou até um valor máximo de 45,19µmolH+·g-1 de tecido as 06:00 mostrando o padrão típico de metabolismo ácido das crassuláceas. O rápido crescimento das raízes, a presença de traqueidas de banda larga e os escassos estomas se interpretaram como adaptações para evitar a dessecação.

Surface wax alkanes were determined in several species of Cactaceae and used as chemotaxonomic characters. Extraction of alkanes was performed with hexane and determination was carried out by GCMS on a data set including 105 species belonging to two subfamilies: Opuntioideae and Cactoideae. The Cactoideae examined were subdivided into seven tribes: Cacteae, Cereeae, Echinocereeae, Notocacteae, Pachycereeae, Rhipsalideae and Trichocereeae. The data obtained were statistically processed using multivariate methods including cluster analysis and discriminant analysis. The results obtained revealed a clear partition among species at both the subfamilial and tribal level, confirming the usefulness of wax alkanes as chemotaxonomic markers in the Cactaceae.

Morpho-anatomy of species in Tribe Pachycereeae seedlings is described and compared with the aim to find differences between the initial growth and establishment stages and to determine the point in time of the change from seedling to young plant. The morpho-anatomical traits were observed from sampling more than 500 seedlings of six species belonging to five genera of this tribe. Seedlings were collected weekly the first three-months after germination and afterwards they were collected monthly to complete 24-months of growth. Statistical differences (P < 0.05) were observed for seedling height, root length, and stem width and height between the species at different ages. A delay in stem and root development was found in Escontria chiotilla and Myrtillocactus geometrizans, species with the smallest seeds. Moreover, the studied species share dermal, fundamental, and vascular tissue traits, however the protein bodies distinguish Pachycereus grandis and the prismatic crystals in epidermis-hypodermis characterize species of Neobuxbaumia. At the onset of vascular cambium, only vessel elements and wide band tracheids become differentiated, whereas fibers appeared in some species after they had one-year of age. We concluded that disappearance of cotyledons, differentiation of ribs, establishment of vascular cambium, a greater accumulation wood, and differentiation of medullary bundles allow us to determine the limits between the seedling stage and the young plant stage.

An analysis of chloroplast DNA restriction site variation was undertaken to investigate the evolutionary divergence of Ferocactus and its possible relationship with North American columnar cacti of tribe Pachycereeae. Our chloroplast DNA study using parsimony-based phylogenetic reconstruction methods provides molecular synapomorphies to define major lineages within Ferocactus and columnar cacti of the tribe Pachycereeae. The issue of monophyly in Ferocactus remains problematic: it appears to be a paraphyletic assemblage derived from an Echinocactus-like ancestor from which three major lineages have evolved. Also, there is a lack of support for the hypothesized basal position of F flavovirens and F robustus, and no evidence was found to favor the phylogenetic relationship of Ferocactus with North American columnar cacti, in particular with Escontria chiotilla. For the columnar cacti, the study supports the monophyly of the tribe Pachycereeae as well as its two subtribes: Stenocereinae and Pachycereinae. In the Stenocereinae, Stenocerelus dumortieri was found to be in a basal position, and forms a phylogenetically distinct lineage from Stenocereus s. str. and other columnar cacti such as Escontria, Polaskia, and Myrtillocactuis. This supports the segregation of S. dumortieri from Stenocereus, and the resurrection of Isolatocereus dumortieri as a distinct genus.

A new heterothallic species of Pichia has been recovered 25 times from widely separated cactus substrates. The organism has been named Pichia opuntiae because the sexually most compatible strains were isolated from Opuntia inermis in Australia. Two varieties are designated based on differences in physiology, habitat, and geographic distribution. P. opuntiae var. opuntiae has a maximum temperature for growth of 30 to 33°C and assimilates citric acid strongly, but assimilation of cellobiose is latent, weak, or negative. P. opuntiae var. thermotolerans grows well at 37°C, but not at 39°C; it assimilates cellobiose strongly but does not assimilate citric acid. Ecologically, P. opuntiae var. opuntiae is associated with Opuntia inermis (tribe Opuntiaeae, subtribe Opuntiinae) in Australia; P. opuntiae var. thermotolerans is associated with species of the cactus tribe Pachycereeae, subtribe Pachycereinae, from various locations in the North American Sonoran Desert. A discussion of the physiological and host-plant shifts for these two varieties and three similar cactophilic yeasts is presented. The base composition of the nuclear deoxyribonucleic acid of P. opuntiae var. opuntiae (average of four strains) is 33.64 ± 0.25 mol% guanine plus cytosine and that of P. opuntiae var. thermotolerans (average of 3 strains) is 33.13 ± 0.23 mol% guanine plus cytosine. The type strain of P. opuntiae and of the type variety, P. opuntiae var. opuntiae, is UCD-FS&T 77-40 (= ATCC 36836 = CBS 7010). The type strain of P. opuntiae var. thermotolerans is UCD-FS&T 76-211 (= ATCC 36834 = CBS 7012).

Since Linnaeus originally described 22 species in the single genus Cactus, over 11,000 binomials and 400 generic names have been proposed for Cactaceae, and the nomenclature of cacti has been in a constant state of change and turmoil. When Engelmann began his cactus studies, only 25 generic names had been proposed, and the family was not well collected. Engelmann described and skillfully illustrated many cacti from the western United States and northernmost Mexico. By 1900, all known columnar species were classified in Cereus Miller; but soon Britton and Rose subdivided this form genus into many smaller and more homogeneous units. The descriptive phase of cactology has slowed, and since Buxbaum researchers have attempted to unravel the evolution of the family and to express phylogenetic information in a generic classification. One area of active phylogenetic research has been in tribe Pachycereeae, which includes the large columnar cacti of Mexico and adjacent areas. These species are often treated as two subtribes: Stenocereinae, which includes species with funicular pigment cells, abundant stem triterpenes, and seeds with verrucose testa having prominent striae; and Pachycereinae, which includes species that lack funicular pigment cells and that often have stem alkaloids but no triterpenes and seeds with smooth testa. New chemical surveys of Stenocereinae have revealed that an individual stem usually has a great number of triterpene glycosides and flavonoids. Crude visual comparisons are made of chromatographic patterns in triterpenes and flavonoids to evaluate existing phylogenetic hypotheses of the species-groups. New reports of alkaloids in Pachycereinae are presented for Lemaireocereus hollianus, Neobuxbaumia mezcalaensis, Pachycereus grandis, and several species of Cephalocereus, but alkaloids are definitely absent in some of the species of Cephalocereus and Neobuxbaumia as well as Mitrocereus. In addition, alkaloids are reported here for the first time in species of Stenocereinae. Cacti are famous for their beautiful flowers and many bizarre vegetative features, but they are equally famous-or infamous-for their nomenclatural and systematic problems, which are, indeed, formidable. Although most botanists are overwhelmed or greatly confused by the taxonomic literature on Cactaceae, some strides have been made to unravel the phylogeny of this family, which includes about 120 genera and 1,550 species (Gibson & Nobel, 1986). Moreover, systematic goals for cacti are no different than those met and addressed in any large and diverse family of plants: 1) to define the limits of each species; 2) to choose the oldest valid binomial; 3) to recognize monophyletic taxa; 4) to define the criteria to be used for erecting each genus; and 5) to produce a truly phylogenetic classification of the genera. This paper examines the problems of producing a phylogenetic classification for cactus genera. Following a brief review on the remarkable taxonomic legacy of Cactaceae, discussions will concentrate on the columnar cacti of tribe Pachycereeae to demonstrate what types of research are needed to solve systematic problems